Nucleotide excision repair endonuclease genes in Drosophila melanogaster

Nucleotide excision repair (NER) is the primary pathway for the removal of ultraviolet light-induced damage and bulky adducts from DNA in eukaryotes. During NER, the helix is unwound around the damaged site, and incisions are made on the 5′ and 3′ sides, to release an oligonucleotide carrying the lesion. Repair synthesis can then proceed, using the intact strand as a template. The incisions flanking the lesion are catalyzed by different structure-specific endonucleases. The 5′ incision is made by a heterodimer of XPF and ERCC1 (Rad1p–Rad10p in Saccharomyces cerevisiae), and the 3′ incision is made by XPG (Rad2p in S. cerevisiae). We previously showed that the DrosophilaXPF homologue is encoded by the meiotic recombination gene mei-9. We report here the identification of the genes encoding the XPG and ERCC1 homologues (XPGDmand ERCC1Dm). XPGDmis encoded by the mus201gene; we found frameshift mutations predicted to produce truncated XPGDmproteins in each of two mus201alleles. These mutations cause defects in nucleotide excision repair and hypersensitivity to alkylating agents and ultraviolet light, but do not cause hypersensitivity to ionizing radiation and do not impair viability or fertility. ERCC1Dminteracts strongly in a yeast two-hybrid assay with MEI-9, indicative of the presumed requirement for these polypeptides to dimerize to form the functional endonuclease. The Drosophila Ercc1gene maps to polytene region 51D1-2. The nucleotide excision repair gene mus210maps nearby (51E-F) but is distinct from Ercc1.